The present invention relates to a fluid storage system and methods of installing the system. Particularly, the invention relates to covered reservoirs for storing water and methods for installing the water storage facility.
Because of environmental problems, such as water runoff from buildings, greenhouses and the like, there is a current need for environmentally safe facilities for storing fluids, e.g., collecting and storing water. That need includes a facility for storing potable water. There are currently many different types of constructions used for fluid storage systems. For example, concrete, masonry, earth and steel reservoirs, as well as embankment tanks, are frequently used for water storage. Other fluids, such as sewage, various types of chemicals and industrial wastes, and the like may be similarly stored in such constructions. With the general exception of large-scale reservoirs used to store water for supplying communities with potable water, storage facilities of these types are usually on a relatively small scale. For example, a water storage facility may cover only several acres of ground.
In storage facilities of this type, a liner is frequently used to line the sides and bottom of the reservoir. For example, flexible thermoplastic elastomer lining material in sheet form and having a thickness on the order of 45 mil, known in the trade as HYPALON.TM., has previously been used for this purpose. It is also customary, and generally necessary in many localities, to provide a cover for the reservoir, e.g., to prevent contamination and evaporation and for safety reasons. The covers for such lined reservoirs have often comprised rigid structures, for example, roofs of reinforced concrete, or other types of relatively rigid building materials. Certain reservoirs, however, have also employed flexible covers, for example, of the same material forming the bottom lining of the reservoir. The use of flexible covers for reservoirs is generally considered a very economical way of covering reservoirs, particularly for those facilities used to store potable water. For example, a flexible cover for a water storage facility precludes contamination of the water with air-borne algae and prevents light necessary to algae growth from reaching the water. Additionally, a cover prevents rodents and other undesirable natural contaminants from entering the stored water.
Those reservoirs having flexible covers, however, have heretofore employed covers which float on the surface of the fluid in the reservoir. The current state of the art in floating covers for reservoirs of this type requires separate floats for maintaining the cover on the surface of the fluid. Additionally, to provide a cover having sufficient material to accommodate the rise and fall of the fluid surface while the cover remains floating on such surface, folds are provided in the cover and weights are applied to the cover to maintain the folds below the fluid surface. While this type of system has been successfully employed, it has certain disadvantages. For example, water runoff from the cover has been a problem and conventionally bilge-type pumps are used to pump the water off the cover. Further, in reservoirs covering acres of land, an individual walking on the floating cover can become trapped within folds of the cover. Such system therefore requires a fence to be placed around the reservoir to warn people away and prevent individuals from being inadvertently trapped within the folds of the cover.
The present invention affords a significant improvement in comparison with such prior fluid storage facilities, especially the type using floating covers, and provides an economical fluid storage system and method of installation which minimize or eliminate the above-noted and other problems with prior fluid storage facilities of this type. Particularly, the present invention provides a fluid storage system having a reservoir with bottom and side and end walls lined with a flexible material and a cover of a flexible material wherein gas under pressure is applied to the space between the fluid level and the cover to maintain the cover in a supported condition spaced above the fluid surface. The cover hereof extends about the reservoir and substantially seals the reservoir from the atmosphere, not only to substantially preclude leakage of air from such pressurized space, but also to prevent contaminants, man-made or of nature, from entering the reservoir. Simultaneously, the predetermined pressurizing system and the pressurized shape of the cover permit natural unassisted runoff of rainwater into a water catchment provided about the periphery of the reservoir. Sufficient rigidity is also afforded the cover to support substantial weight thereon, e.g., individuals walking on the cover.
More particularly, the present invention provides a reservoir having a footing, preferably formed of concrete, about the periphery of the reservoir. The footing mounts a pair of fasteners which extend about the periphery of the reservoir for securing marginal edge portions of both the liner and cover. Each fastener may, for example, comprise a female element secured in the concrete footing for receiving marginal edge portions of the associated cover or liner and a male element received in the female element for securing that marginal edge portion in the female element and to the footing. Consequently, these fasteners, together with the liner and cover, form a substantially air-tight seal about the periphery of the reservoir, although an air-tight seal is not essential.
In accordance with the present invention, a fan is disposed for directing air into and pressurizing the space between the cover and the surface of the fluid in the reservoir. Preferably, the fan is located in the cover. By operating the fan, the air pressure within such space increases sufficiently to displace the cover from and support it above the fluid surface. The cover is maintained in a generally elevated bulbous or dome-like configuration overlying the entirety of the reservoir. Because of the substantially air-tight seal about the periphery of the reservoir and the imperviousness of the cover to transmission of air, fan operation need only be intermittent. Thus, suitable controls are provided the fan for turning the fan on to increase the air pressure within the space below the cover in response to sensing air pressure within the cover below a predetermined air pressure. When the air pressure is raised above a predetermined air pressure, the fan is automatically turned off.
It will be appreciated that the space between the cover and the surface of the fluid is maintained under pressure at all times and sufficiently such that the cover assumes a bulbous or dome-like configuration (dependent upon the plan shape of the reservoir) whereby the cover may support substantial weight, such as the weight of an individual standing on the cover. In accordance with another feature of the present invention, a netting, webbing or other similar flexible structural material is provided over the outside surface of the cover such that, when the cover is under pressure, its shape is maintained by the overlying structural material. For example, where webbing is used, a firs plurality of webs may extend between opposite sides of the reservoir, the web ends being anchored to the footing. A second plurality of webs may similarly be secured to the footing and extend over the cover at right angles to the first plurality of webs. The webs are formed of a material which has a higher tensile strength than the tensile strength of the material forming the cover. Consequently, when the cover is under pressure, it will bear outwardly against the overlying first and second webs whereby the cover is maintained in the predetermined shape, e.g., a bulbous or dome-like shape. This minimizes or eliminates structural loading on the cover and along the fasteners. Substantially the entirety of the structural loading is covered by the overlying material, e.g., the webs. This overlying flexible structural material also assists in maintaining the shape of the cover under high wind loadings which would otherwise distort and possibly even blow out the cover. It will be appreciated that this overlying flexible structural material may take various forms and configurations. For example, high tensile strength fish netting may be used.
This air pressure-sustained shape also directs the flow of rainwater off the cover into a catchment about the periphery of the reservoir. Therefore, in accordance with another feature of the present invention, there is provided a catchment, i.e., a gutter, about the periphery of the reservoir for collecting rainwater runoff from the cover. Where the reservoir is used for water storage, the catchment collects the rainwater runoff from the cover of, flow into the reservoir. Such catchment may take the form of an aluminum gutter secured to the footing about the reservoir or may comprise a shaped concrete catchment or curb in the footing, both of which lie in communication with a drainage system for flowing the rainwater into the reservoir.
An additional feature of the present invention resides in the provision of a pressure relief valve, preferably disposed in the cover. It will be appreciated that the fluid level, e.g., the water level, in the reservoir, rises and falls depending on the quantity of fluid stored. Should the fluid level rise, the pressure in the space between the fluid level surface and the cover will likewise rise. To preclude excessive pressures within such space, the pressure relief valve will open at a predetermined elevated pressure to relieve this excessive pressure.
To construct the fluid storage facility in accordance with the present invention, the liner and cover may be fabricated at a fabrication site removed from the reservoir site. At the reservoir site, both the liner and cover may be disposed in the pre-prepared excavation and secured along their marginal edges. Thereafter, air under pressure may be introduced between the liner and the cover or fluid and air under pressure may be simultaneously introduced whereby the cover will be supported by the contained air within the reservoir.
Where the reservoir is too large for pre-fabrication, the liner and cover material is supplied to the reservoir site in rolls. After the initial excavation and the footings have been constructed, the bottom liner may be rolled out and the edges overlapped for heat-sealing one to the other with an appropriate adhesive. Similarly, the cover may be formed by overlapping the marginal edges of the cover material as the widths of material are unrolled and the edges sealed together. Thus, the overlapping and heat-sealing of the edges may be conducted simultaneously as the cover is pulled from one side of the reservoir across to its opposite side.
Because of the difficulty in dragging a large continuous sheet of rubberized thermoplastic elastomer along an underlying sheet of similar material, there is provided, in accordance with the present invention, a method of installing the cover which overcomes that resistance by enabling the cover to float across the partially or completely filled reservoir. To accomplish this, the rolls of cover material may be overlapped and seamed together, as previously described. However, the leading edge, as well as the side edges of the cover, may be formed into inflatable tubes by folding the cover onto itself. These inflatable tubes may be formed simply by heat-sealing the marginal edges back onto themselves and inflating the space thus formed. These inflated tubes are then disposed in the fluid in the reservoir and the cover may be drawn across the reservoir, with the tubes floating the cover on the surface of the fluid. Upon reaching the opposite side, the tubes may be slit lengthwise, grommets inserted and temporary anchors used to hold the cover in place while the margins of the cover are disposed in the fasteners. By floating the cover across the reservoir, the quantity of material used to form the cover is advantageously reduced in comparison with the quantity of cover material used when the cover is a replication of the liner. That is, the area of the cover may be much less than the area of the liner because the cover need not, for installation, initially conform to the dimensions of the liner.
Accordingly, in a preferred embodiment of the present invention, there is provided a fluid storage system comprising means defining a reservoir for containing a fluid, a cover formed of a flexible, substantially waterproof, material overlying the reservoir and the fluid therein, means disposed about the reservoir for securing the marginal edge portions of the cover about the reservoir, and means for supplying air under pressure between the cover and the surface of the fluid within the reservoir to space and maintain the cover above the fluid surface.
In a further preferred embodiment according to the present invention, there is provided a water storage system comprising means defining a reservoir for containing the water, a cover formed of a flexible, substantially waterproof material for overlying the reservoir and the water therein, a footing formed of a concrete material and disposed substantially about the periphery of the reservoir and means carried by the footing for anchoring marginal edge portions of the cover about the periphery of the reservoir. Means are provided for supplying air under pressure between the cover and the surface of the water in the reservoir to space and maintain the cover above the water surface. Means are also provided overlying the cover and extending between the footings along opposite sides of the reservoir for maintaining the cover in a predetermined shape above the water surface, together with means carried by the footings for anchoring the maintaining means adjacent the opposite sides of the reservoir, the maintaining means being formed of a material having a tensile strength greater than the tensile strength of the flexible cover such that the cover bears against the maintaining means in response to the air pressure against its undersurface whereby the maintaining means maintains the cover in a predetermined shape.
In a still further preferred embodiment according to the present invention, there is provided a method of installing a cover for a fluid storage facility having a reservoir for containing a fluid, including the steps of floating the cover on the fluid in the reservoir from one side of the reservoir to its opposite side such that the cover extends between the opposite sides of the reservoir and supplying air under pressure between the cover and the surface of the fluid to space and maintain the cover above the fluid surface.
Accordingly, it is a primary object of the present invention to provide a novel and improved economical fluid storage facility and methods of construction or installation thereof having various advantages in construction, mode of operation and use, including the capacity to automatically collect rainwater runoff and support substantial weight on the cover, as well as maintain the facility substantially sealed.
These and further objects and advantages of the present invention will become more apparent upon reference to the following specification, appended claims and drawings.